ES2614753T3 - Security item improvements - Google Patents

Abstract

A security element (10) comprising at least one light transmission support substrate (11), a first metal layer (12) having substantially metal-free areas (13) defining indications that are visible in transmitted light, a first partial light scattering layer (14) that provides additional clues that are visible in reflected light, where the first light scattering layer (14) overlaps the substantially metal-free areas (13) in the first metal layer (12).

Description

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DESCRIPTION

Security item improvements

The invention relates to improvements in security elements for use in or on security substrates. In particular, the invention relates to security elements that have public recognition features.

The use in banknotes, passports, certificates and other security documents of security elements, such as security threads or strips, is widely known. These security elements are partially or totally embedded in a paper or plastic substrate and, in general, provide different viewing conditions depending on whether the security document is seen in transmitted or reflected light.

In EP-A-319157, for example, a security element manufactured from a transparent plastic film provided with a continuous reflective metal layer, such as aluminum, which has been deposited in the film is described. The metal layer is partially demetalized to provide clear demetallized regions that form clues. When fully embedded in a paper substrate, the security element is barely visible in reflected light. However, when viewed in transmitted light, the signs can be clearly seen against the dark background of the metallic area of the security element and the adjacent areas of the paper. Such elements can also be used in a security document provided with repeating windows on at least one surface of the paper substrate where the security element is exposed. A security document of this type, seen in transmitted light, will look like a dark line with the highlighted signs. When seen in the light reflected on the side of the windows, the bright parts of bright aluminum are easily visible in the windows. This security element has been very successful in the market and is supplied as the Cleartext® trademark.

For several years, ticketing authorities have been interested in combining the public recognition properties of Cleartext® with the covert properties of a machine-readable feature. To this end, it is preferable to use machine-readable features that can be read using detectors already available to ticketing authorities. Examples of such machine-readable devices are described in WO-A-92/11142 and EP-A-773872.

The security device of WO-A-92/11142 is an attempt to provide this combination. A security device that conforms to this specification has been used commercially with some success. A central region of the safety device has a metallic appearance with clear regions forming characters; On each side of this central strip in the width direction, there are layers of magnetic material with darkening coatings to provide the necessary magnetic component. However, this is a generally unsatisfactory means of achieving the combination of the Cleartext® appearance with the required magnetic properties. The magnetic properties are satisfactory, but the requirement to place the magnetic layers on each side of a central region means that the latter must be relatively narrow with respect to the total width of the security element and results in characters that are small, typically of 0.7 mm in height, and therefore not easily readable. In addition, the structures of the devices described in WO-A-92/11142 are very complex and present substantial problems of lateral registration in the deposit of the various layers; a registration error of even 0.25 mm or the like can allow the presence of the dark magnetic oxide to be evident to the naked eye, thus revealing its presence and seriously damaging the aesthetic appearance of the security element.

A more satisfactory solution, from the point of view of processability, ease of character recognition and aesthetics, will be the manufacture of a device of the type described in EP-A-0319157 from a metal which, in itself, is magnetic. Therefore, the size of the characters and the proportion of the height and width of the characters of the Cleartext® product can be maximized for the benefit of the visibility of the Cleartext® feature, while providing direct compatibility with the magnetic detectors existing.

A means to achieve this is disclosed in Investigation Disclosure No. 323 of March 1991. In this Investigation Disclosure, a magnetic material is deposited on a flexible substrate by spray ford or by other known techniques; non-metallic regions are created by selective printing of a protective layer and subsequent chemical attack. The disclosed magnetic materials may be nickel, cobalt, iron or its alloys, with a preferred combination of cobalt: nickel in the proportion of 85:15%. The disadvantage of this method is that the deposit to the cobalt ford: that in the necessary thickness is a relatively slow and somewhat wasteful process of cobalt, an expensive material. In addition, after this process of deposit to the ford, significant additional processing is required to record the characters. Therefore, the resulting product is relatively expensive.

An additional alternative approach is described in EP A-773872, where a magnetic metal is deposited on a polymer substrate film as the substrate passes through a solution containing the magnetic metal. A preparatory sowing printing operation ensures that the metal

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Magnetic is deposited on the substrate in a chosen pattern, so that when the security product is produced, the magnetic metal on the security element has a specific pattern and provides a visually perceptible security feature and a magnetically detectable security feature. . This method produces a safety element with satisfactory visual and machine readable features. However, manufacturing is not direct and expensive.

An additional approach is detailed in WO-A-9928852. In it, the security device includes a support substrate, a metal layer disposed on the support substrate and a magnetic layer disposed on the metal layer in a substantial register with at least a portion of the metal layer, thus providing characteristics of metallic security and magnetic safety features. The metal layer and the magnetic layer also form graphic or visually identifiable marks on the support substrate to provide a visual security feature. According to one method, the metal layer is applied to the support substrate, the magnetic layer is applied to the metal layer and the layers are etched to form the graphic indications. The magnetic layer may, in one embodiment, include a magnetic chemical resistance that is printed on the metal layer in the form of graphic indications. Again, this method produces a safety element with acceptable visual and magnetic features, but, again, has a high cost with respect to processing and production. It also has color implications for the security element and paper elements that may not always be satisfactory.

Still other alternative solutions are described in WO-A-03091952 and WO-A-03091953. In this case, a security element, comprising a transparent polymeric support layer that carries indications formed from a plurality of opaque and non-opaque regions, is coated with a clear transparent magnetic layer containing a distribution of particles of a material magnetic size and distributed in a concentration, where the magnetic layer remains clear and transparent. However, a problem has been identified with the security elements according to WO-A-03091952 and WO-A-03091953. It has been found that when the security element is embedded in paper, the back of the security element appears as a dark line. This contrasts with other security features of the prior art that are barely visible in reflected light when embedded. It is believed that this dark aspect is the result of the magnetic materials that cause the diffusion of light to a much greater extent, resulting in this diffusion of light to the dark aspect. While this is a matter of limited concern for security elements that are less than 1.6 mm wide, it is of greater concern for wider security elements that are 2 mm or more wide.

Therefore, it is desirable to produce a security element that has magnetic and transmitting properties those described in WO-A-03091953 and WO-A-03091952, but which do not result in the appearance of the rare dark line when embedded on paper. It has now been recognized that the dark appearance can, in fact, provide a very advantageous security benefit. Research activity after this discovery has led to the development of a new class of security element that has a condition of additional reflective vision previously not attainable. It has been found that by selecting materials that have certain properties, it is possible to produce magnetic or non-magnetic security elements with the features of the invention set forth in the claims.

Therefore, the invention provides security elements suitable for embedding all or part of the substrates, the security elements having at least two sets of information that can be seen in reflection of the opposite sides of the substrate.

Therefore, the invention comprises a security element comprising at least one light transmission support substrate, with a first metal layer having substantially metal-free areas defining indications that are visible in transmitted light, a first dispersion layer of partial light that provides additional clues that are visible in reflected light, where the light scattering layer overlaps the substantially metal-free areas in the first metal layer.

The invention will now be described, by way of example only, with reference to the accompanying drawings where:

Figure 1 is a plan view of a partially metallic Cleartext® security element according to the prior art;

Figure 2a is a plan view of a security element according to the present invention;

Figure 2b is a side elevation in cross section of the security element of Figure 2a embedded in a

paper substrate;

Figure 3 is a side elevation in cross section of another security element according to the present invention;

Figure 4 is a side elevation in cross section of an alternative embodiment of the invention;

Figures 5 to 11 are plan views of additional alternative embodiments of the present invention; Y

Figures 12 to 14 are cross-sectional views of additional embodiments of the present invention.

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Figure 1 shows an example of a prior art Cleartext® security element 10. Security element 10 comprises a plastic support substrate that transmits light and water impermeable 11 onto which a metallic aluminum layer is deposited opaque thin 12. The metal layer 12 is then partially removed by a process of demetallization such as, for example, direct etching and strength and etching, to leave areas free of metal or substantially free of metal 13. Such security elements 10 having Negative indications are described in detail in EP-A-319157 and the appropriate demetalization techniques described in EP-A-330733 and US-A-4652015. It has also been suggested that negative metallic indications can be provided using conductive or nonconductive metallic effect inks. Although this is possible, it is not considered to be particularly safe or desirable. For the purposes of the present invention, the use of a metallized and demetallized layer is preferred, although the use of printed metallic effect layers is also recognized. Although it is preferred that the zones 13 be free of metal, it is possible to leave a very thin metal layer, which transmits enough light so that the signs are still visible.

The security feature provided by the security element 10 of the present invention has three elements; a high reflection layer that defines the first indications, a first partial light dispersion layer that forms additional indications and another additional light dispersion layer. The high reflection layer is preferably provided by the metal layer 12 of the security element 10 described above and the additional layers will be described below.

Figure 2a is a plan view of a first embodiment of the present invention where a security element 10 of the type described in EP-A-319157 and illustrated in Figure 1, comprises a support layer 11 provided with a first partial light scattering layer 14 that is present in a localized area, for example as a simple geometric pattern. Figure 2 has been drawn in such a way that the partial light scattering layer 14 and its relation to a demetallized design formed by the metal-free areas 13 can be visualized.

The security element 10 can be partially or totally embedded in a security substrate, such as a paper used to make secure documents, in one of the conventional formats known in the prior art. The fully embedded security element 10 is covered on both sides by the base substrate and the partially embedded element 10 is only partially visible on the surface of the document in the form of a security element with windows. In the last construction, the security element seems to weave in and out of the substrate and is visible in windows on one or both surfaces of the document. In EP-A-0059056 a method for producing paper with so-called window threads can be found. EP-A-0860298 and WO-A-03095188 describe different approaches for inserting more widely exposed elements in a paper substrate. The wide elements, which typically have a width of 2-6 mm, are particularly useful since the surface of the additional exposed element allows better use of optically variable devices, such as those used in the present invention. Security features are now present in many of the world's currencies, as well as vouchers, passports, travelers checks and other documents. In this embodiment, the paper substrate covering the security element provides the additional dispersion layer required.

When the security substrate is seen in transmission, the security element 10 has substantially the same appearance as the Cleartext® element of the prior art, that is, the "PORTALS" negative text reading is highly visible. However, when a windowless side of the substrate is seen in reflection, the observer is able to visualize the geometric pattern formed by the partial light scattering layer 14. The geometric pattern may be related to an impression design that is to be provide on a substrate (where security element 10 is embedded) or may not be related. The present invention benefits from the visualization of the light scattering material and, in addition, retains all the benefits of the known Cleartext® element. The manner in which the partial light scattering layer 14 is applied has to be carefully considered to ensure adequate visualization of the pattern but without the pattern detracting any impression or other information that is subsequently provided on the surface of the substrate.

The visualization of the partial light scattering layer 14 when the security element is provided with an additional light scattering layer can be explained with reference to Figure 2b. Figure 2b shows a part of the security element 10 embedded in a paper substrate 30 such that one side of the security element 10 is exposed in windows 31 on the paper substrate 30 and the other side of the security element 10 is completely covered by the substrate paper 30. In this example, the additional light scattering layer is provided by the paper substrate 30 where the security element 10 is partially embedded.

The incident light on the B side of the security element 10 passes through the paper substrate 30 which acts as the additional light scattering layer where it disperses to a certain extent. When the light is incident on the metal reflection layer 12 not covered by the light scattering layer (interface C), it is reflected back on the paper substrate 30 and then subjected to additional dispersion before exiting the substrate. paper 30. In this case, the light exiting the paper substrate 30 will be more diffuse than the incident on the paper substrate 30 due to the dispersion effect of the paper substrate 30. In addition, the reflected light will have lost some intensity when reflects on the metallic interface C. This could equate, for example, to a 5% intensity loss.

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On the contrary, when the light incident on the partial light scattering layer 14 experiences dispersion when it travels both through the paper substrate 30 and the partial light scattering layer 14. The presence of the partial scattering layer of light 14 will result in a proportion of the light reflected from the metallic interface D that is dispersing backwards towards the metallic interface D and subjecting multiple reflections in the metallic interface D, resulting in a loss of intensity (e.g., 5%), this occurs every time before finally leaving the substrate 30. The combination of the intensity losses generated by the light scattering from the paper substrate 30 and the partial light scattering layer 14 results in a significant reduction in the intensity of the light reflected from the regions of the security element 10, where the partial light scattering layer 14 is present compared to the regions 14a, where the localized light scattering layer 14 is not present. This reduction in intensity results in the indications formed by the partial light scattering layer 14 that appear relatively dark when viewed from the windowless side 33 of the security substrate 32 in Figure 2a.

The additional dispersion layer can also be included in the security device 10 instead of using the dispersion properties of the substrate 30 where it is embedded. For example, it is common practice that the security elements 10 have a width greater than about 2 mm to hide the liner of the security element 10 from the side of the embedded paper using a masking cover over the security element 10. A material suitable for said masking cover is Coates 3188XSN or Coates Heliovyl White S90 353. A typical cover weight is suggested in the region of 2GSM. Said masking cover has dispersion properties similar to those of the paper, so that the light reflected by the security element 10 appears diffused and has a paper-like appearance.

The light scattering layers 14 suitable for use in the present invention include matt varnishes or lacquers and matte etched structures. As noted above, it is possible to provide light scattering layers 14 with additional functionality detectable by machine, for example magnetic properties. Although it should be taken into account that, in this last example, the magnetic materials used and their load in an ink must be carefully controlled to achieve the necessary transparency and readability of the machine.

Any dispersion layer may be used for the additional dispersion layer, including the examples listed below for the light scattering layer 14. However, it is preferred that the additional light scattering layer be sufficiently diffused to Provide a paper-like appearance.

It has been found that a surface coverage for the light scattering layer 14 should be less than 70%, preferably less than 60%, and, more preferably, less than 50% of the total surface area of the thread on one side. For non-magnetic light scattering layers 14, this is predominantly driven by aesthetic considerations. While the coverage of the surface set forth above is adequate to satisfy both the detection requirement by the machine and to provide visibility of the security element 10 in reflection when embedded in paper when magnetic light scattering layers 14 are used. However, even lower surface coverage can be achieved by providing a thicker magnetic scattering layer 14 or increasing the percentage of charge of the magnetic material in the ink used as the magnetic scattering layer 14. The use of a too high surface coverage of the magnetic or non-magnetic light scattering material results in an aspect of the security element 10 as a substantially dark solid line, which is undesirable.

Non-magnetic light scattering layers

In these embodiments of the invention, the dispersion layer 14 takes the form of a varnish or matt lacquer that can be applied using one of the standard security printing procedures. An example of a suitable matte varnish is a suspension of fine particles in an organic resin. The surface particles disperse the light as it passes through the varnish, resulting in a matte appearance. The dispersion process can be improved by the particles that migrate to the surface of the varnish or lacquer when applied to the support 11 or the metallized layer under vacuum 12. The surface particles disperse the light as it passes through the varnish, giving As a result a matt look. Suitable particles include silica-based materials, but it should be recognized that any particulate material could be used that would cause a light to disperse, but not impair the transparency of the coating when applied to the security element 10. An example of A suitable material for forming a light scattering layer 14 is a matte varnish that can be printed on screen comprising 5% of Degussa TS200 silica mattifying agent and 95% of Sericol SX383 solvent based nitrocellulose varnish.

In an alternative solution, the fine particles can be replaced with organic waxes.

As a further alternative, the light scattering layer 14 can be generated by etching a matte structure on the surface of the vacuum metallized layer 12. Such matte structures typically comprise characters or patterns where the surface of the engraving is provided with a rough surface such that the incident light on the surface is reflected in a diffuse non-specular way. As an alternative, the engravings themselves can be

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Lines or points of different angles or sizes distributed so that they create a pattern of light scattering. Magnetic light scattering layers

It has been found that certain new magnetic materials are particularly suitable for the present invention, although this does not exclude the use of more conventional conventional magnetic materials, such as iron oxides (Fe2O3, Fe3O4), barium or strontium ferrites, etc.

The new materials have particular magnetic properties that allow them to distinguish them from other magnetic materials. In particular, these materials have a lower coercivity than conventional iron oxide materials, which means that polarity can be reversed by weaker polarization magnetic fields during the detection process; while they remain magnetically hard, so that they retain the induced magnetism that can then be detected when the article is in a region that is no longer affected by the magnetic polarization field. Typically, these materials can withstand magnetic data in the same manner as conventional magnetic tape.

The new magnetic materials suitable for the security element 10 preferably have a coercivity in the range of 50-150Oe and, more preferably, in the range 70-100Oe. The upper limit of 150Oe could be increased with higher polarization fields. A number of examples of suitable materials include iron, nickel, cobalt and alloys thereof. In this context, the term "alloy" includes materials such as nickel: cobalt, iron: alumino: nickel: cobalt and the like. Nickel materials can be used on scales; In addition, iron flake materials are suitable. Typical nickel scales have lateral dimensions in the range of 5-50 micrometers and a thickness less than 2 micrometers. Typical iron scales have lateral dimensions in the range of 10-30 micrometers and a thickness less than 2 micrometers.

The new preferred materials include iron, nickel and cobalt metal materials (and alloys thereof) that have among the highest inherent magnetizations and, therefore, benefit from the requirement that there is less material in a product to ensure detectability. . Iron is the best of the three with the highest magnetization, but it has been shown that nickel works well from other considerations. These materials are best used in their scale appearance to ensure that they are high-strength hard magnetic materials that can withstand magnetic data if used in a magnetic tape format. This is because nickel and iron, for example, in the form of scales, generally have a high remanence. Flakes and other shaped materials provide an anisotropic (Kforma) defined as:

Kforma _ ° 5 Nd Ms / | -l0

While

Hc at 2.Ktotal / Ms

Which leads to an Hc coercivity that is proportional to Ms and Nd (see, "Magnetism and Magnetic Materials", J P Jakubovics, Uni Press Cambridge, end Ed.)

where

Nd is the factor of the form Ms is the saturation magnetism | J0 is the permeability of the free space Hc is the coercivity

Ktotal is the sum of all K components

However, it should be understood that it may not be essential to take this effect of form into account so that a material exhibits low coercivity and high remanence. For example, the crystalline anisotroph of the materials can also lead to a high remanence, characteristic of strong hard magnetic coercivity, even if the material has a spherical shape, for example cobalt treated oxides.

A new magnetic ink composition suitable for use with the present invention can be obtained from Luminescence Inc as 60681XM.

Conventional magnetic inks, with the common Fe2O3 or Fe3O4 pigments or the like, can be obtained, for example, from Luminescence Inc as RD1790.

The magnetic ink is applied to the security element 10 to form the layer 14 during manufacturing using any of the known printing and transfer techniques, including, for example, gravure, engraving, lithography, on screen and flexography,

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Figure 3 shows a cross section through a security element 10 in accordance with the present invention illustrating a construction for a simple, partially demetallic magnetic device 10.

A first element 10a is first produced by a known demetallization technique as discussed above and comprises a plastic support substrate 11a of polyethylene (PET) and a metal layer 12 with metal-free areas 13. Figure 3 shows a layer protective 15 resulting from a resistance and etching technique, but protective layer 15 will not be present if one of the other techniques described above is used. A second element 10b is produced, which also comprises an impermeable plastic support substrate 11b, such as polyethylene (PET). A partial light scattering layer 14 of a magnetic material is printed on this support substrate 11b, as described above. This partial magnetic light scattering layer 14 can also be printed on the reverse side of the first element 10a; in which case a primer layer may be necessary. In the example shown in Figure 2, the partial light scattering layer 14 has been applied in a cross-pattern. This pattern results in the security element 10 having a magnetic material coverage of less than 50%. The first and second elements 10a, 10b are laminated together to form the security element 10 using a suitable laminating adhesive 16, an example of which is Novacote 10-2525 / 3346. One or more water-based adhesive layers (for example, National Starch & Chemical Eclipse 033-4172) 17 are applied to security element 10 to aid adhesion when embedded in a security substrate 30.

The embodiment of the security element 10 shown in Figure 4 is similar in construction to that illustrated in Figure 3, but without the second support substrate 10b. This is a less expensive construction in terms of materials, but the security element 10 may be more vulnerable to environmental attack during service, unless the correct choices of materials are specified to improve durability. A particular advantage of this is that it makes the production and construction route consistent across the bulk of the types of safety elements and manufacturing routes.

An example of a particularly suitable PET material compatible with this type of simple PET layer design is Mylar 813 from Du Pont, with the pretreated side available for the magnetic light partial dispersion layer 14. This concrete material and others of a similar nature allow externally printed magnetic coatings that are completely durable that withstand the tests of standard conventional safety paper and the requirements of washer durability.

In Figures 3 and 4, the security elements 10 have a white or colored masking cover 18. The presence of the masking cover 18 provides an additional dispersion layer in the structure of the device, which results in the presence of the partial magnetic light dispersion layer 14 that is visualized as a dark image when viewed in reflection from the reverse side of the security element 10. If this security element 10 is subsequently embedded in a paper substrate 30, the visibility of the partial light scattering layer 14 will be further enhanced by the paper dispersion properties. This masking layer 18 may also include fluorescent pigments.

Alternatively, the masking layer 18 can be omitted from the structures since the partial light scattering layer 14 will continue to be visualized when embedded or partially embedded in the paper substrate 30 due to the dispersion properties of the paper.

Figures 6 to 11 show several other examples of how the partial magnetic light scattering layer 14 can be applied to the security element 10. In Figure 6, magnetic material has been applied as a complex geometric pattern. Such patterns can be designed in such a way that they reflect or complement the guiloche patterns commonly used in a wide range of security documents.

In figure 7 a magnetic ink has been printed as repetitive reading of "PORTALS" scripts. This embodiment provides a very strong combination characteristic with the negative script present in the metallic layer 12. In the reflection, an observer will read the positive text "PORTALS" and then, in the transmission, will see the same or a Alternative negative sequence resulting from the demetallized layer 12/13.

In figure 8 a magnetic material in the form of a signature has been applied. This signature can be a monarch, the Governor of a National Bank or, when there is a portrait present on the bill, the signature of the individual portrayed. For banknotes (made of security substrates), the use of the signature of the Governor of the National Bank is preferred, since his signature is also usually printed on the bill. The observer can then compare the signature on the security element 10 with that of the printed surface of the bill.

In Figure 9, the magnetic material has been applied as a solid area with a negative dash present. In this example, the observer visualizes the negative script both in the reflection and in the transmission. As with the previous examples, the script may take any form or design and be the same or different from that provided by the visible demetalized pattern in transmitted light.

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In Figure 10, the magnetic material has been applied as the company logo. As an alternative to company logos, other identification information may be used, such as national badges, animals, flowers, etc. This provides another strong link to the security document and another means to help authenticate the security device to the public.

In Figure 11, the magnetic material is printed to provide denomination information.

Figure 12 shows a detailed cross section through another embodiment of a security element 10 in accordance with the present invention. In this embodiment, the security element 10 is provided with a liquid crystal layer 20. The security element 10 is also provided with a dark absorption layer 21 that cooperates with the liquid crystal layer 20 to provide a strong exchange effect. colored with variable viewing angle. In a preferred example a liquid polymer crystal is used, but an alternative example makes use of liquid crystal inks such as those provided by Sicpa under the Oasis ™ brand. The absorption layer 21 is preferably a dark or black protective layer in the chemical attack of the metal layer 12.

Figure 13 shows a security element 10 provided with a layer of engraving lacquer 22 that is engraved with a diffractive or holographic relief pattern.

Figure 14 shows an embodiment comprising a color dielectric thin film security element 10 having a dielectric layer 24 and absorption layer 25.

As an alternative to printing the light scattering layer 14a, embossed matte light scattering structures can also be used. Embossed matte light scattering structures cause the incident light to be reflected in a non-specular or diffuse manner.

Embossed light scattering structures may comprise lines and take any convenient form, including straight (straight) or curved, such as full or partial arcs of a circle or sections of a sine wave. The lines may be continuous or discontinuous and, for example, be formed by dashes, dots or other shapes. . By other forms it is meant that the points or dashes could have a graphic form. The widths of the line are typically in the range of 10-500 micrometers, preferably 50-300 micrometers. Preferably, the individual lines are barely visible to the naked eye, the main visual impression being given by a series of multiple lines. Lines can define any shape or shape, for example, square, triangle, hexagon, star, flower or signs, such as a letter or a number.

Embossed lmea structures are preferably formed by applying an embossing plate to the security element with heat and pressure. Preferably, the embossing process is a gravure printing process and is carried out using a gravure plate having recesses that define the lmea structures. Preferably, the security element is embossed blindly, that is, the recesses are not filled with ink.

The height of the embossed areas should be at least 2 pm but, preferably, greater than 5 pm and, more preferably, greater than 10 pm.

In a further embodiment of the present invention, the security device is incorporated into a polymer banknote. Polymeric banknotes, such as those described in WO-A-8300659, are formed from a transparent substrate comprising at least one layer of an opacifying coating on both sides of the substrate. The opacifying coating is omitted in areas located on both sides of the substrate to form a transparent region known as a window. In this embodiment of the present invention, the security device is formed in a selected area on the transparent substrate of the polymer banknote by applying a metal layer and a first layer of light scattering in the same manner as described above. In this way, the transparent substrate of the polymer banknote also acts as the light transmission support substrate for the security device. The opacifying coating is then applied to the transparent polymeric substrate on the security device and functions as the additional layer of light scattering.

Polymer banknotes are just one example of a secure document based on a polymeric substrate, the present invention is equally applicable to other types of polymeric secure documents.

Claims (23)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 60 65 1. A security element (10) comprising at least one light transmission support substrate (11), a first metal layer (12) having substantially metal-free areas (13) defining indications that are visible in light transmitted, a first partial light scattering layer (14) that provides additional clues that are visible in reflected light, where the first light scattering layer (14) overlaps the substantially metal-free areas (13) in the first metal layer (12). 2. A security element (10) according to claim 1, further comprising a second light scattering layer (14, 30) that at least partially overlaps the first light scattering layer (14). 3. A security element (10) according to claim 1 or claim 2, wherein the first light scattering layer (14) and the metal layer (12) are applied to opposite sides of the at least one support substrate (11 ). 4. A security element (10) according to claim 1, comprising a second support substrate (11b) to which the first light scattering layer (14) is applied before the two support substrates (11a, 11b ) laminate together. A security element (10) according to any one of the preceding claims, wherein the surface area coverage of the first light scattering layer (14) is less than 70%, more preferably less than 60% and, more preferably , less than 50%. A security element (10) according to any one of the preceding claims, wherein one or both layers of light scattering (14, 30) are a matt varnish layer. 7. A security element (10) according to any one of claims 1 to 8, wherein one or both layers of light scattering (14, 30) is a lacquer layer. A security element (10) according to any one of claims 1 to 5, wherein one or both layers of light scattering (14, 30) are provided by a matte embossing structure. 9. A security element (10) according to any one of claims 1 to 5, wherein one or both layers of light scattering (14, 30) is a magnetic layer. 10. A security element (10) according to claim 9, wherein the material of the magnetic layer has a coercivity in the range of 50 to 150 Oe and, preferably, in the range of 70 to 100 Oe. 11. A security element (10) according to claim 9 or claim 10, wherein the magnetic layer comprises an iron, nickel, cobalt material or an alloy of iron, nickel and / or cobalt. 12. A security element (10) according to claim 11, wherein the magnetic layer comprises an iron flake material. 13. A security element (10) according to claim 11, wherein the magnetic layer comprises a metal flake material. 14. A security element (10) according to any one of claims 9 to 13, wherein the magnetic layer is a magnetic ink. 15. A security element (10) according to any one of the preceding claims, wherein the indications provided by the first light scattering layer (14) comprise a geometric pattern, or alphanumeric information, or a signature or pictorial indications. 16. A security element (10) according to any one of the preceding claims, wherein the first light scattering layer (14) is applied in a cross-pattern configuration having a surface coverage of less than 50%. 17. A security element (10) according to any one of the preceding claims, further comprising a liquid crystal layer (20) and a dark absorption layer (21) cooperating with the liquid crystal layer (20) to provide a color change effect by varying the angle of vision. 18. A security element (10) according to any one of claims 1 to 16, wherein the security element (10) is provided with a layer of embossed lacquer (22) which is embossed with a pattern of diffractive or holographic relief. 19. A security element (10) according to any one of claims 1 to 16, wherein the security element (10) comprises a thin dielectric metal film to provide a color change effect. 20. A security substrate (30) comprising a security element (10) according to any one of the preceding 5 claims, at least partially embedded therein. 21. A security substrate (30) comprising a security element (10) at least partially embedded therein, wherein said security element comprises at least one light transmission support substrate (11), a first metal layer (12) that has substantially metal-free areas (13) that define indications that 10 are visible in transmitted light, a partial light scattering layer (14) that provides additional clues that are visible in reflected light, where the light scattering layer (14) overlaps the substantially metal free areas (13) in the first metal layer (12), where the security substrate (30) forms an additional light scattering layer that at least partially overlaps the first light scattering layer (14) of the security element (10). fifteen 22. A security document formed from a security substrate (30) according to claim 20 or claim 21. 23. A security document according to claim 22, comprising a voucher, a tax stamp, an authentication label, a passport, a check, a certificate, an identity card, a banknote or the like.